Leo XIII was the 256th pope of the Roman Catholic Church, serving from 1878 until his death in 1903. He was a highly respected pontiff, known for his intellectualism and progressive views on social issues. Synonyms for the term "Leo XIII" include "Pope Leo XIII," "Gioacchino Pecci" (his birth name), and "the Good Pope." During his tenure, Leo XIII issued a number of important encyclicals, including Rerum Novarum, which addressed the rights of workers, and Immortale Dei, which dealt with the relationship between church and state. His legacy as a leading figure in the modernization of the Catholic Church continues to be felt today.